Slow edit when using subdivision modifier
Why do you need 5 subdivision levels while you are editing an object?
With each level, your geometry is getting subdivided, creating more vertices: out of every quad at least 4 virtual quads will be created per level of subdivision. A single quad, subdivided to level 5, will result in 1089 vertices, 2112 edges and 1024 faces.
Blender will of course be slow when you have that many vertices, but you shouldn't need that big of a subdivision surface. First of all, if the object has Shade Smooth on, you probably won't even see a difference between 4 and 5 subdivision levels.
Also, you will notice that there is both a View and a Render number of subdivisions:

So, as in the image above, I have only 2 subdivision levels while I am working one the model, so it is fast, but when I render the image with my model, it changes to be 5 subdivision levels so it looks good but isn't slow while I am working.
So, the solution is that you don't need to make your machine faster, you can just use less subdivision levels while working.